Previous work has led to the development of a variety of human tumor xenograft models applicable to various subsets of the in vitro cell line panels including: intraperitoneal survival models; subrenal capsule assay models; subcutaneous tumor models; orthotopic tumor models; and, a single practical metastatic tumor model. However, due to the scope of the current screening panels (60 individual tumor cell lines representing seven major tumor types) and the wide variety of behaviors they display upon transplantation into athymic mice, it has not been feasible to develop a comprehensive set of models for each cell line. In this continuing project, we are developing tumor models (leading through a rational challenge hierarchy) on an individualized basis, and applying them to the evaluation of selected high-priority anticancer drug screening leads from LDDRD research. Because of the critical importance of metastatic disease to cancer chemotherapy, we are continuing efforts to develop additional metastatic models based on the human tumor cell lines used for in vitro screening.